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    <title>Document</title>
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    <script>
        // 思想就是要交互变量的这个理念，引出temp来
        let num1 = 10
        let num2 = 20
        let temp
        temp = num1
        num1 = num2
        num2 = temp
        console.log(num1, num2)
    </script>
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